text: /* linenoise.c -- guerrilla line editing library against the idea that a
   * line editing lib needs to be 20,000 lines of C code.
   *
   * You can find the latest source code at:
   *
   *   http://github.com/antirez/linenoise
   *
   * Does a number of crazy assumptions that happen to be true in 99.9999% of
   * the 2010 UNIX computers around.
   *
   * ------------------------------------------------------------------------
   *
   * Copyright (c) 2010-2016, Salvatore Sanfilippo <antirez at gmail dot com>
   * Copyright (c) 2010-2013, Pieter Noordhuis <pcnoordhuis at gmail dot com>
   *
   * All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions are
   * met:
   *
   *  *  Redistributions of source code must retain the above copyright
   *     notice, this list of conditions and the following disclaimer.
   *
   *  *  Redistributions in binary form must reproduce the above copyright
   *     notice, this list of conditions and the following disclaimer in the
   *     documentation and/or other materials provided with the distribution.
   *
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
   * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
   * HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
   * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
   * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
   * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   *
   * ------------------------------------------------------------------------
   *
   * References:
   * - http://invisible-island.net/xterm/ctlseqs/ctlseqs.html
   * - http://www.3waylabs.com/nw/WWW/products/wizcon/vt220.html
   *
   * Todo list:
   * - Filter bogus Ctrl+<char> combinations.
   * - Win32 support
   *
   * Bloat:
   * - History search like Ctrl+r in readline?
   *
   * List of escape sequences used by this program, we do everything just
   * with three sequences. In order to be so cheap we may have some
   * flickering effect with some slow terminal, but the lesser sequences
   * the more compatible.
   *
   * EL (Erase Line)
   *    Sequence: ESC [ n K
   *    Effect: if n is 0 or missing, clear from cursor to end of line
   *    Effect: if n is 1, clear from beginning of line to cursor
   *    Effect: if n is 2, clear entire line
   *
   * CUF (CUrsor Forward)
   *    Sequence: ESC [ n C
   *    Effect: moves cursor forward n chars
   *
   * CUB (CUrsor Backward)
   *    Sequence: ESC [ n D
   *    Effect: moves cursor backward n chars
   *
   * The following is used to get the terminal width if getting
   * the width with the TIOCGWINSZ ioctl fails
   *
   * DSR (Device Status Report)
   *    Sequence: ESC [ 6 n
   *    Effect: reports the current cusor position as ESC [ n ; m R
   *            where n is the row and m is the column
   *
   * When multi line mode is enabled, we also use an additional escape
   * sequence. However multi line editing is disabled by default.
   *
   * CUU (Cursor Up)
   *    Sequence: ESC [ n A
   *    Effect: moves cursor up of n chars.
   *
   * CUD (Cursor Down)
   *    Sequence: ESC [ n B
   *    Effect: moves cursor down of n chars.
   *
   * When linenoiseClearScreen() is called, two additional escape sequences
   * are used in order to clear the screen and position the cursor at home
   * position.
   *
   * CUP (Cursor position)
   *    Sequence: ESC [ H
   *    Effect: moves the cursor to upper left corner
   *
   * ED (Erase display)
   *    Sequence: ESC [ 2 J
   *    Effect: clear the whole screen
   *
   */
  
  #include <termios.h>
  #include <unistd.h>
  #include <stdlib.h>
  #include <stdio.h>
  #include <errno.h>
  #include <string.h>
  #include <stdlib.h>
  #include <ctype.h>
  #include <sys/stat.h>
  #include <sys/types.h>
  #include <sys/ioctl.h>
  #include <unistd.h>
  #include "linenoise.h"
  
  #define LINENOISE_DEFAULT_HISTORY_MAX_LEN 100
  #define LINENOISE_MAX_LINE 4096
  static char *unsupported_term[] = {"dumb","cons25","emacs",NULL};
  static linenoiseCompletionCallback *completionCallback = NULL;
  static linenoiseHintsCallback *hintsCallback = NULL;
  static linenoiseFreeHintsCallback *freeHintsCallback = NULL;
  
  static struct termios orig_termios; /* In order to restore at exit.*/
  static int maskmode = 0; /* Show "***" instead of input. For passwords. */
  static int rawmode = 0; /* For atexit() function to check if restore is needed*/
  static int mlmode = 0;  /* Multi line mode. Default is single line. */
  static int atexit_registered = 0; /* Register atexit just 1 time. */
  static int history_max_len = LINENOISE_DEFAULT_HISTORY_MAX_LEN;
  static int history_len = 0;
  //记录历史命令行
  static char **history = NULL;
  
  /* The linenoiseState structure represents the state during line editing.
   * We pass this state to functions implementing specific editing
   * functionalities. */
  struct linenoiseState {
      int ifd;            /* Terminal stdin file descriptor. */
      int ofd;            /* Terminal stdout file descriptor. */
      char *buf;          /* Edited line buffer. */
      size_t buflen;      /* Edited line buffer size. */
      const char *prompt; /* Prompt to display. */
      size_t plen;        /* Prompt length. */
      size_t pos;         /* Current cursor position. */
      size_t oldpos;      /* Previous refresh cursor position. */
      size_t len;         /* Current edited line length. */
      size_t cols;        /* Number of columns in terminal. */
      size_t maxrows;     /* Maximum num of rows used so far (multiline mode) */
      int history_index;  /* The history index we are currently editing. */
  };
  
  enum KEY_ACTION{
  	KEY_NULL = 0,	    /* NULL */
  	CTRL_A = 1,         /* Ctrl+a */
  	CTRL_B = 2,         /* Ctrl-b */
  	CTRL_C = 3,         /* Ctrl-c */
  	CTRL_D = 4,         /* Ctrl-d */
  	CTRL_E = 5,         /* Ctrl-e */
  	CTRL_F = 6,         /* Ctrl-f */
  	CTRL_H = 8,         /* Ctrl-h */
  	TAB = 9,            /* Tab */
  	CTRL_K = 11,        /* Ctrl+k */
  	CTRL_L = 12,        /* Ctrl+l */
  	ENTER = 13,         /* Enter */
  	CTRL_N = 14,        /* Ctrl-n */
  	CTRL_P = 16,        /* Ctrl-p */
  	CTRL_T = 20,        /* Ctrl-t */
  	CTRL_U = 21,        /* Ctrl+u */
  	CTRL_W = 23,        /* Ctrl+w */
  	ESC = 27,           /* Escape */
  	BACKSPACE =  127    /* Backspace */
  };
  
  static void linenoiseAtExit(void);
  int linenoiseHistoryAdd(const char *line);
  static void refreshLine(struct linenoiseState *l);
  
  /* Debugging macro. */
  #if 0
  FILE *lndebug_fp = NULL;
  #define lndebug(...) \
      do { \
          if (lndebug_fp == NULL) { \
              lndebug_fp = fopen("/tmp/lndebug.txt","a"); \
              fprintf(lndebug_fp, \
              "[%d %d %d] p: %d, rows: %d, rpos: %d, max: %d, oldmax: %d\n", \
              (int)l->len,(int)l->pos,(int)l->oldpos,plen,rows,rpos, \
              (int)l->maxrows,old_rows); \
          } \
          fprintf(lndebug_fp, ", " __VA_ARGS__); \
          fflush(lndebug_fp); \
      } while (0)
  #else
  #define lndebug(fmt, ...)
  #endif
  
  /* ======================= Low level terminal handling ====================== */
  
  /* Enable "mask mode". When it is enabled, instead of the input that
   * the user is typing, the terminal will just display a corresponding
   * number of asterisks, like "****". This is useful for passwords and other
   * secrets that should not be displayed. */
  void linenoiseMaskModeEnable(void) {
      maskmode = 1;
  }
  
  /* Disable mask mode. */
  void linenoiseMaskModeDisable(void) {
      maskmode = 0;
  }
  
  /* Set if to use or not the multi line mode. */
  void linenoiseSetMultiLine(int ml) {
      mlmode = ml;
  }
  
  /* Return true if the terminal name is in the list of terminals we know are
   * not able to understand basic escape sequences. */
  static int isUnsupportedTerm(void) {
      char *term = getenv("TERM");
      int j;
  
      if (term == NULL) return 0;
      for (j = 0; unsupported_term[j]; j++)
          if (!strcasecmp(term,unsupported_term[j])) return 1;
      return 0;
  }
  
  /* Raw mode: 1960 magic shit. */
  static int enableRawMode(int fd) {
      struct termios raw;
  
      if (!isatty(STDIN_FILENO)) goto fatal;
      if (!atexit_registered) {
          atexit(linenoiseAtExit);
          atexit_registered = 1;
      }
      if (tcgetattr(fd,&orig_termios) == -1) goto fatal;
  
      raw = orig_termios;  /* modify the original mode */
      /* input modes: no break, no CR to NL, no parity check, no strip char,
       * no start/stop output control. */
      raw.c_iflag &= ~(BRKINT | ICRNL | INPCK | ISTRIP | IXON);
      /* output modes - disable post processing */
      raw.c_oflag &= ~(OPOST);
      /* control modes - set 8 bit chars */
      raw.c_cflag |= (CS8);
      /* local modes - choing off, canonical off, no extended functions,
       * no signal chars (^Z,^C) */
      raw.c_lflag &= ~(ECHO | ICANON | IEXTEN | ISIG);
      /* control chars - set return condition: min number of bytes and timer.
       * We want read to return every single byte, without timeout. */
      raw.c_cc[VMIN] = 1; raw.c_cc[VTIME] = 0; /* 1 byte, no timer */
  
      /* put terminal in raw mode after flushing */
      if (tcsetattr(fd,TCSAFLUSH,&raw) < 0) goto fatal;
      rawmode = 1;
      return 0;
  
  fatal:
      errno = ENOTTY;
      return -1;
  }
  
  static void disableRawMode(int fd) {
      /* Don't even check the return value as it's too late. */
      if (rawmode && tcsetattr(fd,TCSAFLUSH,&orig_termios) != -1)
          rawmode = 0;
  }
  
  /* Use the ESC [6n escape sequence to query the horizontal cursor position
   * and return it. On error -1 is returned, on success the position of the
   * cursor. */
  static int getCursorPosition(int ifd, int ofd) {
      char buf[32];
      int cols, rows;
      unsigned int i = 0;
  
      /* Report cursor location */
      if (write(ofd, "\x1b[6n", 4) != 4) return -1;
  
      /* Read the response: ESC [ rows ; cols R */
      while (i < sizeof(buf)-1) {
          if (read(ifd,buf+i,1) != 1) break;
          if (buf[i] == 'R') break;
          i++;
      }
      buf[i] = '\0';
  
      /* Parse it. */
      if (buf[0] != ESC || buf[1] != '[') return -1;
      if (sscanf(buf+2,"%d;%d",&rows,&cols) != 2) return -1;
      return cols;
  }
  
  /* Try to get the number of columns in the current terminal, or assume 80
   * if it fails. */
  static int getColumns(int ifd, int ofd) {
      struct winsize ws;
  
      if (ioctl(1, TIOCGWINSZ, &ws) == -1 || ws.ws_col == 0) {
          /* ioctl() failed. Try to query the terminal itself. */
          int start, cols;
  
          /* Get the initial position so we can restore it later. */
          start = getCursorPosition(ifd,ofd);
          if (start == -1) goto failed;
  
          /* Go to right margin and get position. */
          if (write(ofd,"\x1b[999C",6) != 6) goto failed;
          cols = getCursorPosition(ifd,ofd);
          if (cols == -1) goto failed;
  
          /* Restore position. */
          if (cols > start) {
              char seq[32];
              snprintf(seq,32,"\x1b[%dD",cols-start);
              if (write(ofd,seq,strlen(seq)) == -1) {
                  /* Can't recover... */
              }
          }
          return cols;
      } else {
          return ws.ws_col;
      }
  
  failed:
      return 80;
  }
  
  /* Clear the screen. Used to handle ctrl+l */
  void linenoiseClearScreen(void) {
      if (write(STDOUT_FILENO,"\x1b[H\x1b[2J",7) <= 0) {
          /* nothing to do, just to avoid warning. */
      }
  }
  
  /* Beep, used for completion when there is nothing to complete or when all
   * the choices were already shown. */
  static void linenoiseBeep(void) {
      fprintf(stderr, "\x7");
      fflush(stderr);
  }
  
  /* ============================== Completion ================================ */
  
  /* Free a list of completion option populated by linenoiseAddCompletion(). */
  static void freeCompletions(linenoiseCompletions *lc) {
      size_t i;
      for (i = 0; i < lc->len; i++)
          free(lc->cvec[i]);
      if (lc->cvec != NULL)
          free(lc->cvec);
  }
  
  /* This is an helper function for linenoiseEdit() and is called when the
   * user types the <tab> key in order to complete the string currently in the
   * input.
   *
   * The state of the editing is encapsulated into the pointed linenoiseState
   * structure as described in the structure definition. */
  static int completeLine(struct linenoiseState *ls) {
      linenoiseCompletions lc = { 0, NULL };
      int nread, nwritten;
      char c = 0;
  
      completionCallback(ls->buf,&lc);
      if (lc.len == 0) {
          linenoiseBeep();
      } else {
          size_t stop = 0, i = 0;
  
          while(!stop) {
              /* Show completion or original buffer */
              if (i < lc.len) {
                  struct linenoiseState saved = *ls;
  
                  ls->len = ls->pos = strlen(lc.cvec[i]);
                  ls->buf = lc.cvec[i];
                  refreshLine(ls);
                  ls->len = saved.len;
                  ls->pos = saved.pos;
                  ls->buf = saved.buf;
              } else {
                  refreshLine(ls);
              }
  
              nread = read(ls->ifd,&c,1);
              if (nread <= 0) {
                  freeCompletions(&lc);
                  return -1;
              }
  
              switch(c) {
                  case 9: /* tab */
                      i = (i+1) % (lc.len+1);
                      if (i == lc.len) linenoiseBeep();
                      break;
                  case 27: /* escape */
                      /* Re-show original buffer */
                      if (i < lc.len) refreshLine(ls);
                      stop = 1;
                      break;
                  default:
                      /* Update buffer and return */
                      if (i < lc.len) {
                          nwritten = snprintf(ls->buf,ls->buflen,"%s",lc.cvec[i]);
                          ls->len = ls->pos = nwritten;
                      }
                      stop = 1;
                      break;
              }
          }
      }
  
      freeCompletions(&lc);
      return c; /* Return last read character */
  }
  
  /* Register a callback function to be called for tab-completion. */
  void linenoiseSetCompletionCallback(linenoiseCompletionCallback *fn) {
      completionCallback = fn;
  }
  
  /* Register a hits function to be called to show hits to the user at the
   * right of the prompt. */
  void linenoiseSetHintsCallback(linenoiseHintsCallback *fn) {
      hintsCallback = fn;
  }
  
  /* Register a function to free the hints returned by the hints callback
   * registered with linenoiseSetHintsCallback(). */
  void linenoiseSetFreeHintsCallback(linenoiseFreeHintsCallback *fn) {
      freeHintsCallback = fn;
  }
  
  /* This function is used by the callback function registered by the user
   * in order to add completion options given the input string when the
   * user typed <tab>. See the example.c source code for a very easy to
   * understand example. */
  void linenoiseAddCompletion(linenoiseCompletions *lc, const char *str) {
      size_t len = strlen(str);
      char *copy, **cvec;
  
      copy = malloc(len+1);
      if (copy == NULL) return;
      memcpy(copy,str,len+1);
      cvec = realloc(lc->cvec,sizeof(char*)*(lc->len+1));
      if (cvec == NULL) {
          free(copy);
          return;
      }
      lc->cvec = cvec;
      lc->cvec[lc->len++] = copy;
  }
  
  /* =========================== Line editing ================================= */
  
  /* We define a very simple "append buffer" structure, that is an heap
   * allocated string where we can append to. This is useful in order to
   * write all the escape sequences in a buffer and flush them to the standard
   * output in a single call, to avoid flickering effects. */
  struct abuf {
      char *b;
      int len;
  };
  
  static void abInit(struct abuf *ab) {
      ab->b = NULL;
      ab->len = 0;
  }
  
  static void abAppend(struct abuf *ab, const char *s, int len) {
      char *new = realloc(ab->b,ab->len+len);
  
      if (new == NULL) return;
      memcpy(new+ab->len,s,len);
      ab->b = new;
      ab->len += len;
  }
  
  static void abFree(struct abuf *ab) {
      free(ab->b);
  }
  
  /* Helper of refreshSingleLine() and refreshMultiLine() to show hints
   * to the right of the prompt. */
  void refreshShowHints(struct abuf *ab, struct linenoiseState *l, int plen) {
      char seq[64];
      if (hintsCallback && plen+l->len < l->cols) {
          int color = -1, bold = 0;
          char *hint = hintsCallback(l->buf,&color,&bold);
          if (hint) {
              int hintlen = strlen(hint);
              int hintmaxlen = l->cols-(plen+l->len);
              if (hintlen > hintmaxlen) hintlen = hintmaxlen;
              if (bold == 1 && color == -1) color = 37;
              if (color != -1 || bold != 0)
                  snprintf(seq,64,"\033[%d;%d;49m",bold,color);
              else
                  seq[0] = '\0';
              abAppend(ab,seq,strlen(seq));
              abAppend(ab,hint,hintlen);
              if (color != -1 || bold != 0)
                  abAppend(ab,"\033[0m",4);
              /* Call the function to free the hint returned. */
              if (freeHintsCallback) freeHintsCallback(hint);
          }
      }
  }
  
  /* Single line low level line refresh.
   *
   * Rewrite the currently edited line accordingly to the buffer content,
   * cursor position, and number of columns of the terminal. */
  static void refreshSingleLine(struct linenoiseState *l) {
      char seq[64];
      size_t plen = strlen(l->prompt);
      int fd = l->ofd;
      char *buf = l->buf;
      size_t len = l->len;
      size_t pos = l->pos;
      struct abuf ab;
  
      while((plen+pos) >= l->cols) {
          buf++;
          len--;
          pos--;
      }
      while (plen+len > l->cols) {
          len--;
      }
  
      abInit(&ab);
      /* Cursor to left edge */
      snprintf(seq,64,"\r");
      abAppend(&ab,seq,strlen(seq));
      /* Write the prompt and the current buffer content */
      abAppend(&ab,l->prompt,strlen(l->prompt));
      if (maskmode == 1) {
          while (len--) abAppend(&ab,"*",1);
      } else {
          abAppend(&ab,buf,len);
      }
      /* Show hits if any. */
      refreshShowHints(&ab,l,plen);
      /* Erase to right */
      snprintf(seq,64,"\x1b[0K");
      abAppend(&ab,seq,strlen(seq));
      /* Move cursor to original position. */
      snprintf(seq,64,"\r\x1b[%dC", (int)(pos+plen));
      abAppend(&ab,seq,strlen(seq));
      if (write(fd,ab.b,ab.len) == -1) {} /* Can't recover from write error. */
      abFree(&ab);
  }
  
  /* Multi line low level line refresh.
   *
   * Rewrite the currently edited line accordingly to the buffer content,
   * cursor position, and number of columns of the terminal. */
  static void refreshMultiLine(struct linenoiseState *l) {
      char seq[64];
      int plen = strlen(l->prompt);
      int rows = (plen+l->len+l->cols-1)/l->cols; /* rows used by current buf. */
      int rpos = (plen+l->oldpos+l->cols)/l->cols; /* cursor relative row. */
      int rpos2; /* rpos after refresh. */
      int col; /* colum position, zero-based. */
      int old_rows = l->maxrows;
      int fd = l->ofd, j;
      struct abuf ab;
  
      /* Update maxrows if needed. */
      if (rows > (int)l->maxrows) l->maxrows = rows;
  
      /* First step: clear all the lines used before. To do so start by
       * going to the last row. */
      abInit(&ab);
      if (old_rows-rpos > 0) {
          lndebug("go down %d", old_rows-rpos);
          snprintf(seq,64,"\x1b[%dB", old_rows-rpos);
          abAppend(&ab,seq,strlen(seq));
      }
  
      /* Now for every row clear it, go up. */
      for (j = 0; j < old_rows-1; j++) {
          lndebug("clear+up");
          snprintf(seq,64,"\r\x1b[0K\x1b[1A");
          abAppend(&ab,seq,strlen(seq));
      }
  
      /* Clean the top line. */
      lndebug("clear");
      snprintf(seq,64,"\r\x1b[0K");
      abAppend(&ab,seq,strlen(seq));
  
      /* Write the prompt and the current buffer content */
      abAppend(&ab,l->prompt,strlen(l->prompt));
      if (maskmode == 1) {
          unsigned int i;
          for (i = 0; i < l->len; i++) abAppend(&ab,"*",1);
      } else {
          abAppend(&ab,l->buf,l->len);
      }
  
      /* Show hits if any. */
      refreshShowHints(&ab,l,plen);
  
      /* If we are at the very end of the screen with our prompt, we need to
       * emit a newline and move the prompt to the first column. */
      if (l->pos &&
          l->pos == l->len &&
          (l->pos+plen) % l->cols == 0)
      {
          lndebug("<newline>");
          abAppend(&ab,"\n",1);
          snprintf(seq,64,"\r");
          abAppend(&ab,seq,strlen(seq));
          rows++;
          if (rows > (int)l->maxrows) l->maxrows = rows;
      }
  
      /* Move cursor to right position. */
      rpos2 = (plen+l->pos+l->cols)/l->cols; /* current cursor relative row. */
      lndebug("rpos2 %d", rpos2);
  
      /* Go up till we reach the expected positon. */
      if (rows-rpos2 > 0) {
          lndebug("go-up %d", rows-rpos2);
          snprintf(seq,64,"\x1b[%dA", rows-rpos2);
          abAppend(&ab,seq,strlen(seq));
      }
  
      /* Set column. */
      col = (plen+(int)l->pos) % (int)l->cols;
      lndebug("set col %d", 1+col);
      if (col)
          snprintf(seq,64,"\r\x1b[%dC", col);
      else
          snprintf(seq,64,"\r");
      abAppend(&ab,seq,strlen(seq));
  
      lndebug("\n");
      l->oldpos = l->pos;
  
      if (write(fd,ab.b,ab.len) == -1) {} /* Can't recover from write error. */
      abFree(&ab);
  }
  
  /* Calls the two low level functions refreshSingleLine() or
   * refreshMultiLine() according to the selected mode. */
  static void refreshLine(struct linenoiseState *l) {
      if (mlmode)
          refreshMultiLine(l);
      else
          refreshSingleLine(l);
  }
  
  /* Insert the character 'c' at cursor current position.
   *
   * On error writing to the terminal -1 is returned, otherwise 0. */
  int linenoiseEditInsert(struct linenoiseState *l, char c) {
      if (l->len < l->buflen) {
          if (l->len == l->pos) {
              l->buf[l->pos] = c;
              l->pos++;
              l->len++;
              l->buf[l->len] = '\0';
              if ((!mlmode && l->plen+l->len < l->cols && !hintsCallback)) {
                  /* Avoid a full update of the line in the
                   * trivial case. */
                  char d = (maskmode==1) ? '*' : c;
                  if (write(l->ofd,&d,1) == -1) return -1;
              } else {
                  refreshLine(l);
              }
          } else {
              memmove(l->buf+l->pos+1,l->buf+l->pos,l->len-l->pos);
              l->buf[l->pos] = c;
              l->len++;
              l->pos++;
              l->buf[l->len] = '\0';
              refreshLine(l);
          }
      }
      return 0;
  }
  
  /* Move cursor on the left. */
  void linenoiseEditMoveLeft(struct linenoiseState *l) {
      if (l->pos > 0) {
          l->pos--;
          refreshLine(l);
      }
  }
  
  /* Move cursor on the right. */
  void linenoiseEditMoveRight(struct linenoiseState *l) {
      if (l->pos != l->len) {
          l->pos++;
          refreshLine(l);
      }
  }
  
  /* Move cursor to the start of the line. */
  void linenoiseEditMoveHome(struct linenoiseState *l) {
      if (l->pos != 0) {
          l->pos = 0;
          refreshLine(l);
      }
  }
  
  /* Move cursor to the end of the line. */
  void linenoiseEditMoveEnd(struct linenoiseState *l) {
      if (l->pos != l->len) {
          l->pos = l->len;
          refreshLine(l);
      }
  }
  
  /* Substitute the currently edited line with the next or previous history
   * entry as specified by 'dir'. */
  #define LINENOISE_HISTORY_NEXT 0
  #define LINENOISE_HISTORY_PREV 1
  void linenoiseEditHistoryNext(struct linenoiseState *l, int dir) {
      if (history_len > 1) {
          /* Update the current history entry before to
           * overwrite it with the next one. */
          free(history[history_len - 1 - l->history_index]);
          history[history_len - 1 - l->history_index] = strdup(l->buf);
          /* Show the new entry */
          l->history_index += (dir == LINENOISE_HISTORY_PREV) ? 1 : -1;
          if (l->history_index < 0) {
              l->history_index = 0;
              return;
          } else if (l->history_index >= history_len) {
              l->history_index = history_len-1;
              return;
          }
          strncpy(l->buf,history[history_len - 1 - l->history_index],l->buflen);
          l->buf[l->buflen-1] = '\0';
          l->len = l->pos = strlen(l->buf);
          refreshLine(l);
      }
  }
  
  /* Delete the character at the right of the cursor without altering the cursor
   * position. Basically this is what happens with the "Delete" keyboard key. */
  void linenoiseEditDelete(struct linenoiseState *l) {
      if (l->len > 0 && l->pos < l->len) {
          memmove(l->buf+l->pos,l->buf+l->pos+1,l->len-l->pos-1);
          l->len--;
          l->buf[l->len] = '\0';
          refreshLine(l);
      }
  }
  
  /* Backspace implementation. */
  void linenoiseEditBackspace(struct linenoiseState *l) {
      if (l->pos > 0 && l->len > 0) {
          memmove(l->buf+l->pos-1,l->buf+l->pos,l->len-l->pos);
          l->pos--;
          l->len--;
          l->buf[l->len] = '\0';
          refreshLine(l);
      }
  }
  
  /* Delete the previosu word, maintaining the cursor at the start of the
   * current word. */
  void linenoiseEditDeletePrevWord(struct linenoiseState *l) {
      size_t old_pos = l->pos;
      size_t diff;
  
      while (l->pos > 0 && l->buf[l->pos-1] == ' ')
          l->pos--;
      while (l->pos > 0 && l->buf[l->pos-1] != ' ')
          l->pos--;
      diff = old_pos - l->pos;
      memmove(l->buf+l->pos,l->buf+old_pos,l->len-old_pos+1);
      l->len -= diff;
      refreshLine(l);
  }
  
  /* This function is the core of the line editing capability of linenoise.
   * It expects 'fd' to be already in "raw mode" so that every key pressed
   * will be returned ASAP to read().
   *
   * The resulting string is put into 'buf' when the user type enter, or
   * when ctrl+d is typed.
   *
   * The function returns the length of the current buffer. */
  //读取一行数据，支持简单的shell命令
  static int linenoiseEdit(int stdin_fd, int stdout_fd, char *buf, size_t buflen, const char *prompt)
  {
      struct linenoiseState l;
  
      /* Populate the linenoise state that we pass to functions implementing
       * specific editing functionalities. */
      l.ifd = stdin_fd;
      l.ofd = stdout_fd;
      l.buf = buf;
      l.buflen = buflen;
      l.prompt = prompt;
      l.plen = strlen(prompt);
      l.oldpos = l.pos = 0;
      l.len = 0;
      l.cols = getColumns(stdin_fd, stdout_fd);
      l.maxrows = 0;
      l.history_index = 0;
  
      /* Buffer starts empty. */
      l.buf[0] = '\0';
      l.buflen--; /* Make sure there is always space for the nulterm */
  
      /* The latest history entry is always our current buffer, that
       * initially is just an empty string. */
      linenoiseHistoryAdd("");
  
      if (write(l.ofd,prompt,l.plen) == -1) return -1;
      while(1) {
          char c;
          int nread;
          char seq[3];
  
          nread = read(l.ifd,&c,1);
          if (nread <= 0) return l.len;
  
          /* Only autocomplete when the callback is set. It returns < 0 when
           * there was an error reading from fd. Otherwise it will return the
           * character that should be handled next. */
          if (c == 9 && completionCallback != NULL) {
              c = completeLine(&l);
              /* Return on errors */
              if (c < 0) return l.len;
              /* Read next character when 0 */
              if (c == 0) continue;
          }
  
          switch(c) {
          case ENTER:    /* enter */
              history_len--;
              free(history[history_len]);
              if (mlmode) linenoiseEditMoveEnd(&l);
              if (hintsCallback) {
                  /* Force a refresh without hints to leave the previous
                   * line as the user typed it after a newline. */
                  linenoiseHintsCallback *hc = hintsCallback;
                  hintsCallback = NULL;
                  refreshLine(&l);
                  hintsCallback = hc;
              }
              return (int)l.len;
          case CTRL_C:     /* ctrl-c */
              errno = EAGAIN;
              return -1;
          case BACKSPACE:   /* backspace */
          case 8:     /* ctrl-h */
              linenoiseEditBackspace(&l);
              break;
          case CTRL_D:     /* ctrl-d, remove char at right of cursor, or if the
                              line is empty, act as end-of-file. */
              if (l.len > 0) {
                  linenoiseEditDelete(&l);
              } else {
                  history_len--;
                  free(history[history_len]);
                  return -1;
              }
              break;
          case CTRL_T:    /* ctrl-t, swaps current character with previous. */
              if (l.pos > 0 && l.pos < l.len) {
                  int aux = buf[l.pos-1];
                  buf[l.pos-1] = buf[l.pos];
                  buf[l.pos] = aux;
                  if (l.pos != l.len-1) l.pos++;
                  refreshLine(&l);
              }
              break;
          case CTRL_B:     /* ctrl-b */
              linenoiseEditMoveLeft(&l);
              break;
          case CTRL_F:     /* ctrl-f */
              linenoiseEditMoveRight(&l);
              break;
          case CTRL_P:    /* ctrl-p */
              linenoiseEditHistoryNext(&l, LINENOISE_HISTORY_PREV);
              break;
          case CTRL_N:    /* ctrl-n */
              linenoiseEditHistoryNext(&l, LINENOISE_HISTORY_NEXT);
              break;
          case ESC:    /* escape sequence */
              /* Read the next two bytes representing the escape sequence.
               * Use two calls to handle slow terminals returning the two
               * chars at different times. */
              if (read(l.ifd,seq,1) == -1) break;
              if (read(l.ifd,seq+1,1) == -1) break;
  
              /* ESC [ sequences. */
              if (seq[0] == '[') {
                  if (seq[1] >= '0' && seq[1] <= '9') {
                      /* Extended escape, read additional byte. */
                      if (read(l.ifd,seq+2,1) == -1) break;
                      if (seq[2] == '~') {
                          switch(seq[1]) {
                          case '3': /* Delete key. */
                              linenoiseEditDelete(&l);
                              break;
                          }
                      }
                  } else {
                      switch(seq[1]) {
                      case 'A': /* Up */
                          linenoiseEditHistoryNext(&l, LINENOISE_HISTORY_PREV);
                          break;
                      case 'B': /* Down */
                          linenoiseEditHistoryNext(&l, LINENOISE_HISTORY_NEXT);
                          break;
                      case 'C': /* Right */
                          linenoiseEditMoveRight(&l);
                          break;
                      case 'D': /* Left */
                          linenoiseEditMoveLeft(&l);
                          break;
                      case 'H': /* Home */
                          linenoiseEditMoveHome(&l);
                          break;
                      case 'F': /* End*/
                          linenoiseEditMoveEnd(&l);
                          break;
                      }
                  }
              }
  
              /* ESC O sequences. */
              else if (seq[0] == 'O') {
                  switch(seq[1]) {
                  case 'H': /* Home */
                      linenoiseEditMoveHome(&l);
                      break;
                  case 'F': /* End*/
                      linenoiseEditMoveEnd(&l);
                      break;
                  }
              }
              break;
          default:
              if (linenoiseEditInsert(&l,c)) return -1;
              break;
          case CTRL_U: /* Ctrl+u, delete the whole line. */
              buf[0] = '\0';
              l.pos = l.len = 0;
              refreshLine(&l);
              break;
          case CTRL_K: /* Ctrl+k, delete from current to end of line. */
              buf[l.pos] = '\0';
              l.len = l.pos;
              refreshLine(&l);
              break;
          case CTRL_A: /* Ctrl+a, go to the start of the line */
              linenoiseEditMoveHome(&l);
              break;
          case CTRL_E: /* ctrl+e, go to the end of the line */
              linenoiseEditMoveEnd(&l);
              break;
          case CTRL_L: /* ctrl+l, clear screen */
              linenoiseClearScreen();
              refreshLine(&l);
              break;
          case CTRL_W: /* ctrl+w, delete previous word */
              linenoiseEditDeletePrevWord(&l);
              break;
          }
      }
      return l.len;
  }
  
  /* This special mode is used by linenoise in order to print scan codes
   * on screen for debugging / development purposes. It is implemented
   * by the linenoise_example program using the --keycodes option. */
  void linenoisePrintKeyCodes(void) {
      char quit[4];
  
      printf("Linenoise key codes debugging mode.\n"
              "Press keys to see scan codes. Type 'quit' at any time to exit.\n");
      if (enableRawMode(STDIN_FILENO) == -1) return;
      memset(quit,' ',4);
      while(1) {
          char c;
          int nread;
  
          nread = read(STDIN_FILENO,&c,1);
          if (nread <= 0) continue;
          memmove(quit,quit+1,sizeof(quit)-1); /* shift string to left. */
          quit[sizeof(quit)-1] = c; /* Insert current char on the right. */
          if (memcmp(quit,"quit",sizeof(quit)) == 0) break;
  
          printf("'%c' %02x (%d) (type quit to exit)\n",
              isprint(c) ? c : '?', (int)c, (int)c);
          printf("\r"); /* Go left edge manually, we are in raw mode. */
          fflush(stdout);
      }
      disableRawMode(STDIN_FILENO);
  }
  
  /* This function calls the line editing function linenoiseEdit() using
   * the STDIN file descriptor set in raw mode. */
  static int linenoiseRaw(char *buf, size_t buflen, const char *prompt) {
      int count;
  
      if (buflen == 0) {
          errno = EINVAL;
          return -1;
      }
  
      if (enableRawMode(STDIN_FILENO) == -1) return -1;
      count = linenoiseEdit(STDIN_FILENO, STDOUT_FILENO, buf, buflen, prompt);
      disableRawMode(STDIN_FILENO);
      printf("\n");
      return count;
  }
  
  /* This function is called when linenoise() is called with the standard
   * input file descriptor not attached to a TTY. So for example when the
   * program using linenoise is called in pipe or with a file redirected
   * to its standard input. In this case, we want to be able to return the
   * line regardless of its length (by default we are limited to 4k). */
  static char *linenoiseNoTTY(void) {
      char *line = NULL;
      size_t len = 0, maxlen = 0;
  
      while(1) {
          if (len == maxlen) {
              if (maxlen == 0) maxlen = 16;
              maxlen *= 2;
              char *oldval = line;
              line = realloc(line,maxlen);
              if (line == NULL) {
                  if (oldval) free(oldval);
                  return NULL;
              }
          }
          int c = fgetc(stdin);
          if (c == EOF || c == '\n') {
              if (c == EOF && len == 0) {
                  free(line);
                  return NULL;
              } else {
                  line[len] = '\0';
                  return line;
              }
          } else {
              line[len] = c;
              len++;
          }
      }
  }
  
  /* The high level function that is the main API of the linenoise library.
   * This function checks if the terminal has basic capabilities, just checking
   * for a blacklist of stupid terminals, and later either calls the line
   * editing function or uses dummy fgets() so that you will be able to type
   * something even in the most desperate of the conditions. */
  char *linenoise(const char *prompt) {
      char buf[LINENOISE_MAX_LINE];
      int count;
  
      if (!isatty(STDIN_FILENO)) {
          /* Not a tty: read from file / pipe. In this mode we don't want any
           * limit to the line size, so we call a function to handle that. */
          return linenoiseNoTTY();
      } else if (isUnsupportedTerm()) {
          //不支持的终端
          size_t len;
  
          printf("%s",prompt);
          fflush(stdout);
          if (fgets(buf,LINENOISE_MAX_LINE,stdin) == NULL) return NULL;
          len = strlen(buf);
          while(len && (buf[len-1] == '\n' || buf[len-1] == '\r')) {
              len--;
              buf[len] = '\0';
          }
          return strdup(buf);
      } else {
          count = linenoiseRaw(buf,LINENOISE_MAX_LINE,prompt);
          if (count == -1) return NULL;
          return strdup(buf);
      }
  }
  
  /* This is just a wrapper the user may want to call in order to make sure
   * the linenoise returned buffer is freed with the same allocator it was
   * created with. Useful when the main program is using an alternative
   * allocator. */
  void linenoiseFree(void *ptr) {
      free(ptr);
  }
  
  /* ================================ History ================================= */
  
  /* Free the history, but does not reset it. Only used when we have to
   * exit() to avoid memory leaks are reported by valgrind & co. */
  static void freeHistory(void) {
      if (history) {
          int j;
  
          for (j = 0; j < history_len; j++)
              free(history[j]);
          free(history);
      }
  }
  
  /* At exit we'll try to fix the terminal to the initial conditions. */
  static void linenoiseAtExit(void) {
      disableRawMode(STDIN_FILENO);
      freeHistory();
  }
  
  /* This is the API call to add a new entry in the linenoise history.
   * It uses a fixed array of char pointers that are shifted (memmoved)
   * when the history max length is reached in order to remove the older
   * entry and make room for the new one, so it is not exactly suitable for huge
   * histories, but will work well for a few hundred of entries.
   *
   * Using a circular buffer is smarter, but a bit more complex to handle. */
  //将命令加入到history中
  int linenoiseHistoryAdd(const char *line) {
      char *linecopy;
  
      if (history_max_len == 0) return 0;
  
      /* Initialization on first call. */
      //初始化历史命令行变量
      if (history == NULL) {
          history = malloc(sizeof(char*)*history_max_len);
          if (history == NULL) return 0;
          memset(history,0,(sizeof(char*)*history_max_len));
      }
  
      /* Don't add duplicated lines. */
      //跳过与上一行重复的命令
      if (history_len && !strcmp(history[history_len-1], line)) return 0;
  
      /* Add an heap allocated copy of the line in the history.
       * If we reached the max length, remove the older line. */
      linecopy = strdup(line);
      if (!linecopy) return 0;
      //达到命令行最大数，移除第一条，并执行memmove(这里搞成环形队列好一些，省memmove)
      if (history_len == history_max_len) {
          free(history[0]);
          memmove(history,history+1,sizeof(char*)*(history_max_len-1));
          history_len--;
      }
      //将历史命令存入
      history[history_len] = linecopy;
      history_len++;
      return 1;
  }
  
  /* Set the maximum length for the history. This function can be called even
   * if there is already some history, the function will make sure to retain
   * just the latest 'len' elements if the new history length value is smaller
   * than the amount of items already inside the history. */
  int linenoiseHistorySetMaxLen(int len) {
      char **new;
  
      if (len < 1) return 0;
      if (history) {
          int tocopy = history_len;
  
          new = malloc(sizeof(char*)*len);
          if (new == NULL) return 0;
  
          /* If we can't copy everything, free the elements we'll not use. */
          if (len < tocopy) {
              int j;
  
              for (j = 0; j < tocopy-len; j++) free(history[j]);
              tocopy = len;
          }
          memset(new,0,sizeof(char*)*len);
          memcpy(new,history+(history_len-tocopy), sizeof(char*)*tocopy);
          free(history);
          history = new;
      }
      history_max_len = len;
      if (history_len > history_max_len)
          history_len = history_max_len;
      return 1;
  }
  
  /* Save the history in the specified file. On success 0 is returned
   * otherwise -1 is returned. */
  int linenoiseHistorySave(const char *filename) {
      mode_t old_umask = umask(S_IXUSR|S_IRWXG|S_IRWXO);
      FILE *fp;
      int j;
  
      fp = fopen(filename,"w");
      umask(old_umask);
      if (fp == NULL) return -1;
      chmod(filename,S_IRUSR|S_IWUSR);
      for (j = 0; j < history_len; j++)
          fprintf(fp,"%s\n",history[j]);
      fclose(fp);
      return 0;
  }
  
  /* Load the history from the specified file. If the file does not exist
   * zero is returned and no operation is performed.
   *
   * If the file exists and the operation succeeded 0 is returned, otherwise
   * on error -1 is returned. */
  //加载filename中的命令，将其加入到history中
  int linenoiseHistoryLoad(const char *filename) {
      FILE *fp = fopen(filename,"r");
      char buf[LINENOISE_MAX_LINE];
  
      if (fp == NULL) return -1;
  
      while (fgets(buf,LINENOISE_MAX_LINE,fp) != NULL) {
          char *p;
  
          p = strchr(buf,'\r');
          if (!p) p = strchr(buf,'\n');
          if (p) *p = '\0';
          linenoiseHistoryAdd(buf);
      }
      fclose(fp);
      return 0;
  }
  